Google has said its Android mobile operating system is not part of the lawsuit that Apple has filed against HTC.

The iPod manufacturer has claimed that HTC, maker of the flagship Android handset Nexus One, has infringed 20 patents; Google says that “We are not a party to this lawsuit. However, we stand behind our Android operating system and the partners who have helped us to develop it."

The patents Apple’s suit cites range from 1995 to February this year; in a detailed breakdown on blog Engadget, writer Nilay Patel says “this litigation will take years and require many hearing [sic] to determine exactly what's covered”.

Although some alleged infringements cover Windows Mobile phones and others cover Android phones, there are attacks on HTC’s software and hardware.

The software HTC’s Android handsets run, however, is built with Google.

HTC itself, which is the world’s largest maker of Android phones, told the Taiwanese stock exchange that it “is not only a mobile technology innovator, [we] also hold a large number of patents."

The company will work with the American justice system to protect its own innovations and rights, it added, saying that it does not consider the Apple lawsuit will trouble its business. HTC stock fell 2pc, however.